In the related art, a mobile communication terminal test apparatus that tests transmit/receive characteristics of a mobile communication terminal is known. The mobile communication terminal test apparatus includes a transmit unit that transmits a signal to the mobile communication terminal and a receive unit that receives a signal from the mobile communication terminal and performs a test for the corresponding mobile communication terminal by operating as a pseudo base station and transmitting/receiving a signal to/from the mobile communication terminal.
As a test item of the mobile communication terminal, an error vector magnitude (EVM) measurement that measures a positional difference between a measurement modulation signal and an ideal modulation signal within the signal band (hereinafter, referred to as a “band channel”) from the mobile communication terminal is known.
For example, Patent Document 1 discloses a mobile communication terminal test apparatus that measures a signal level from the mobile communication terminal.
On the other hand, according to Long Term Evolution (LTE) which is a next generation mobile communication standard, a plurality of channel widths (1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, or 20 MHz) is defined as a 3GPP standard.
According to the LTE, a frequency division multiple access (FDMA) scheme is employed as a communication scheme. As a result, communication among a plurality of mobile communication terminals is multiplexed through a single channel (hereinafter, referred to as a “transmission channel, wherein the bandwidth of the transmission channel will be referred to as a “transmission channel width”) used in the communication in practice within the band channel. Therefore, a single mobile communication terminal rarely uses the entire frequency band of a single transmission channel, and communication is made by allocating a part of the frequency band of a single transmission channel to a single mobile communication terminal. Such a band allocation is performed on a resource block (RB)-by-RB basis.
Specifically, in the LTE system, a bundle of data having a frequency range of a unitary frequency band width ΔF (e.g., ΔF=12 subcarriers) and a unitary time width (e.g., ΔT=0, 5 ms=1 slot=7 symbols) is set to a resource block (RB), and a block of a unitary time width ΔT and a frequency bandwidth nΔF (where n denotes any integer equal to or larger than 1) formed on an RB-by-RB basis (hereinafter, referred to as a “current block,” wherein in the case of n=1, a current block is equal to the RB) is transmitted by changing a digital communication signal in a hopping manner on a frequency-time domain as time elapses. In other words, a frequency F having a frequency band of F to F+nΔF (a frequency range of the current block) and a value of n representing the magnitude of the bandwidth are changed for every unitary time width ΔT. However, it is possible that the frequency F changes for every twice the unitary time width ΔT (2 slots).
In addition to the frequency for every unitary time width ΔT, transmission is made by defining transmission conditions such as a modulation scheme, a transmission rate, transmission power (they are together known as “transmission information”). Such changes in the transmission information are performed by controlling a station to obtain a transmission quality depending on a propagation status.
In addition, a part of the aforementioned transmission information is embedded in a data format that defines a digital communication signal. Hereinafter, the data format will be described. A digital signal is transmitted using a data format shown in FIG. 7. In FIG. 7, a single frame includes 10 subframes for 10 ms (milliseconds). Among them, P-SS (first synchronization signal) or S-SS (second synchronization signal) are included in the 0th and 5th subframes. Each subframe includes a plurality of RBs. As shown in FIG. 7(b), each RB constitutes a single slot along the time axis, and a single slot includes 7 items of symbol data along the time axis. A single RB includes 12 subcarriers along the vertical axis as shown in FIG. 7(b). The subcarriers are set at an interval of 15 kHz. In addition, for the RB, data embedded in each symbol are determined as shown in FIGS. 7(b) and 7(c). In FIGS. 7(b) and 7(c), the primary synchronization signal (P-SS) and the secondary synchronization signal (S-SS) are the first and second synchronization signals, respectively, used to transmit or receive digital signals in synchronization. In addition, a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), and a reference signal (RS) are provided. Among them, the PDCCH includes control information for controlling the RB and a modulation scheme of PDSCH (e.g., QPSK modulation, 16-QAM, 64-QAM, and the like). In the PDSCH, user data are included and modulated based on the modulation scheme controlled by the PDCCH. In addition, the modulation scheme is changed to obtain a transmission quality under the propagation conditions and the like at that time. The RS is also referred to as a reference signal and used as a reference signal when the receiver apparatus in the wireless terminal (mobile station) side performs demodulation or used in equalization of the propagation path.
In the uplink, as a modulation scheme, the SC-FDMA is used. According to the SC-FDMA, communication is performed by converting each subcarrier of the frequency domain into symbols of the time domain. Then, the symbols included in a single slot along the time domain (7 symbols included in a single slot) are referred to as “time-oriented symbols,” and the symbols obtained by converting each subcarrier from the frequency-domain to the time domain are referred to as “frequency-oriented symbols.” In addition, in the case of simply referring to a “symbol”, it is assumed that a single symbol is designated by a frequency-oriented symbol position and a time-oriented symbol position.
[Related Art Document]
[Patent Document]
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-46431